Automatic transmission synchronous gear shift

Abstract

A method of commanding a synchronous gear shift begins by receiving a request to shift from a third gear to a first gear, and skipping a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear. Subsequently the method includes: reducing a torque command to a predetermined value; opening a clutch disposed on the input shaft of the transmission to decouple the transmission from the engine; transitioning the engine from a torque-control mode into a speed-control mode; commanding the engine to rotate at a speed dictated by the motion of the vehicle and the gear ratio of the first gear; closing the clutch to couple the transmission and the engine; and transitioning the engine back into the torque-control mode.

The invention claimed is: 
     
       1. A method of commanding a synchronous gear shift in a vehicle powertrain that includes an engine and a transmission having a plurality of ordered gears, the method comprising:
 receiving a request to shift from a third gear to a first gear, and skipping a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear; 
 reducing a torque command to a predetermined value; 
 opening a clutch disposed on an input shaft of the transmission to decouple the transmission from the engine; 
 transitioning the engine from a torque-control mode into a speed-control mode; 
 commanding the engine, while in the speed-control mode, to rotate at a speed dictated by the motion of the vehicle and the gear ratio of the first gear; 
 closing the clutch to couple the transmission and the engine; and 
 transitioning the engine back into the torque-control mode. 
 
     
     
       2. The method of  claim 1 , wherein the engine operates in response to a driver torque request while in the torque-control mode; and
 wherein closing the clutch to couple the transmission and the engine includes closing the clutch over a period of time such that a torque of the input shaft of the transmission is blended to match the driver torque request. 
 
     
     
       3. The method of  claim 2 , further comprising receiving the driver torque request continuously throughout the synchronous gear shift. 
     
     
       4. The method of  claim 3 , further comprising arbitrating between the driver torque request and a transmission input shaft speed request. 
     
     
       5. The method of  claim 1 , wherein the torque command saturates at an immediate torque maximum during the speed-control mode, and wherein the immediate torque maximum includes a maximum amount of torque capable of being produced by the engine at a fixed airflow. 
     
     
       6. The method of  claim 1 , wherein the torque command approaches zero prior to the closing of the clutch to couple the transmission and the engine. 
     
     
       7. The method of  claim 1 , wherein the torque command and the engine rotation speed are independently controllable through the adjustment of a spark timing, a fuel supply, and an airflow supply. 
     
     
       8. The method of  claim 1 , further comprising disregarding an axle torque request while in the speed-control mode. 
     
     
       9. The method of  claim 1 , wherein transitioning the engine back into the torque-control mode includes gradually transitioning the engine back into the torque-control mode over a period of time. 
     
     
       10. The method of  claim 1 , wherein the torque command is a function of a driver acceleration request when the engine is in the torque-control mode. 
     
     
       11. A method of commanding a synchronous gear shift in a vehicle powertrain that includes an engine and a transmission having a plurality of ordered gears, the method comprising:
 receiving a request to shift from a third gear to a first gear, and skipping a second gear having a gear ratio between the gear ratio of the first gear and the gear ratio of the third gear; 
 reducing a torque command to approximately zero via an immediate torque request; 
 opening a clutch disposed on an input shaft of the transmission to decouple the transmission from the engine; 
 transitioning the engine from a torque-control mode into a speed-control mode; 
 disregarding an axle torque request while in the speed-control mode. 
 commanding the engine, while in the speed-control mode, to rotate at a speed dictated by the motion of the vehicle and the gear ratio of the first gear; 
 closing the clutch to couple the transmission and the engine; and 
 transitioning the engine back into the torque-control mode. 
 
     
     
       12. The method of  claim 11 , wherein an immediate torque request effectuates a modification to at least one of a spark timing and an amount of fuel supplied to a cylinder. 
     
     
       13. The method of  claim 11 , wherein the torque command saturates at an immediate torque maximum during the speed-control mode, and wherein the immediate torque maximum includes a maximum amount of torque capable of being produced by the engine at a fixed airflow. 
     
     
       14. The method of  claim 11 , wherein the torque command approaches zero prior to the closing of the clutch to couple the transmission and the engine. 
     
     
       15. The method of  claim 11 , wherein the torque command and the engine rotation speed are independently controllable through the adjustment of a spark timing, a fuel supply, and an airflow supply. 
     
     
       16. The method of  claim 11 , wherein transitioning the engine back into the torque-control mode includes gradually transitioning the engine back into the torque-control mode over a period of time. 
     
     
       17. The method of  claim 11 , wherein the torque command is a function of a driver acceleration request when the engine is in the torque-control mode.